Commonwealth Electricity Company is a wholly-owned subsidiary of Commonwealth Energy System. The company generates transmits and sells electricity in 40 communities in southeastern Massachusetts, Cape Cod and the island of Martha's Vineyard. During the year 1998 the comany sold all of the generating assets. The company has approximately 329,000 retail customers including 44,600 seasonal customers. In 1999 the company merged with BEC Energy to form NSTAR as a holding company.